Chemical Equilibrium
aA + bB→cC + dD
If A and B is reacted will reach a point where there’s no change more advanced, this point called equilibrium.
Chemical equilibrium is a dynamic equilibrium. Species in the reaction straight form in a constant manner, but without changed totality in the system of concentration.
Chemical equilibrium happens when we have reversible reaction in a closed system. There’s no mater which can be added or can be taken from that system except energy. In equilibrium, the number of something which in the mixed is constant although reaction still take place. This happens may be because the velocities of reaction to the right and to the left are same.
Equilibrium’s law
The value of multiplied balance concentration of substances at right part of reaction divided to the value of multiplied balance concentration of substance at left part of reaction, both of them is raised to a power with them coefficient of reaction, will have a constant value in constant temperature.
Constants equilibrium
a. Formulation of constant equilibrium based on concentration [Kc]
Every steps with certain concentration can be calculated the value of Q using methode compare the value of Q with Kc.
Z Q <>c : formation reaction of product will take place
Z Q <>c : didn’t happen changes, happen equilibrium
Z Q <>c : analyzing reaction of product to be reagen will take place
1. Homogen equilibrium reaction
Homogeny equilibrium reaction is a reaction which all substance phases in equilibrium condition for all same reaction.
pA[g] + qB[g] <=> rC [g] + sD[g]
Kc = M[r+s]-[p+q] M = molarity
2. Heterogenic equilibrium reaction
In heterogenic equilibrium reaction, concentration substances with phase solid and liquid are not calculated. This is because concentration of solid substance is considered constant. Determinate of Kc:
a. Mixed between gas with solid, which is calculated is gas
b. Mixed between aqueous with solid, which is calculated is aqueous.
pA[g] + qB[s] <=> rC [g] + sD[g]
Equilibrium shift
1. Concentration changes
Reaction:
A + B→C
If A plus means that the concentration is enlarged, so that "if given, he would give" the shift to the right so that the C lot. If B is taken (separate) minimize the concentration of B means that "if taken, he would take" the reaction shifts to the left so that C decreases.
If one substance concentration is enlarged (plus), then the reaction shifts from the substance. If one substance concentration is reduced (reduced), then the reaction will shift toward substance.
2. Temperature changes
If the temperature is increased (adding or provide heat) then the reaction will shift to the left of the reaction endothermic (required). If the temperature is lowered (less heat), then the reaction will shift to the right of the direction exothermic reaction (issued).
For example: 2NH3 N2 + 3H2 ΔH = +92 Kj
If the temperature is increased the reaction shifts to the right (NH3 many loose), if the temperature is lowered will shift to the left.
ZTemperature increase will increasing the value of Kc for system with positive DHrks [endotherm]
ZTemperature increase will decreasing the value of Kc for system with negative DHrks [endotherm]
3. Pressure changes
The change affects only the pressure for the gas. Solid and liquid phase pressure effects are ignored.
Boyle's law according to the:
If the pressure is enlarged (reduced volume) then the reaction shifts toward the number of moles of gas is the smallest.
If the pressure is reduced (enlarged volume) then the reaction shifts toward the number of moles of the largest gas.
Because the coefficient of the reaction mole ratio states, it is sufficient to consider the amount of gas on the coefficient of each segment.
4. Catalyst rule
Catalyst is a substance that can accelerate the reaction but did not come to react.
In accordance with the reaction function will accelerate the achievement faster equilibrium process, the way forward and accelerate the reaction as big backlash.
Catalytic function at the beginning of the reaction (before equilibrium is reached).
If the speed of forward reaction = rate through the catalytic reaction stopped functioning.
Dissociation Equilibrium
Dissociation is the action of analyzing a substance to be the other substance which is simpler. Dissociation can happen by heating or usually called thermal dissociation. Dissociation which take place in the closed room will finish with an equilibrium which called dissociation equilibrium.
The large of fraction substance which is dissociated is clarified by dissociation’s degree [a], that is the comparson between number of substance which is dissociated with number of substance before [n].
The number of mole substance which is dissociated = a · n
Equilibrium Systems in Industry
Haber-Bosch process:
1. Is a very important process in the chemical industry because ammonia is the main ingredient in the manufacture of various products such as urea, nitric acid, and nitrogen compounds.
2. Can be used as a solvent for liquid ammonia polarity nearly matching polarity water.
Contact Process :
Is the process of making sulfuric acid on a large scale. Used for the manufacture of ammonium sulphate fertilizer, the oil refining process, the steel industry to remove rust before the steel coated with tin or zinc, in making pigments, pharmaceuticals, metals refining process by electrolysis, the textile industry, etc.
In the contact process materials used are pure sulfur is burned in the air:
S + O2 → SO2
SO2 is oxidized in air formed by using a catalyst:
2 SO2 + O2 → 2SO3 + 45 kcal
The catalyst used is vanadium pentaoxide. The lower the temperature the more SO3 produced, but the reaction is slow. Taking into account the time factor and the selected temperature of 400oC in approximately 98%. SO3 difficult because soluble in water then reconstituted concentrated H2SO4.
SO3 + H2SO4 → H2S2O7 (pirosulfat acid)
H2S2O7 + H2O → 2H2SO4
0 komentar:
Posting Komentar